Local increase of ovarian steroid hormone concentration in blood supplyingthe oviduct and uterus during early pregnancy of sows

Countercurrent transfer in the ovarian vascular pedicle elevates the concen tration of steroid hormones in blood supplying the oviduct and periovarian part of the uterus during the estrous cycle in the pig. This study was cond ucted to determine whether during early pregnancy the arterial blood supply to the oviduct and uterus carries greater concentration of steroid hormone than systemic blood. The concentration of ovarian steroid hormones (proges terone, estradiol-17 beta, estrone, androstenedione and testosterone) was m easured in 40 gilts on Days 12, 18, 25 or 35 of pregnancy. Silastic cathete rs were inserted: a) into the jugular vein, b) into the branch of uterine a rtery close to the ovary (proximal to the ovary) and c) into the branch of the uterine artery close to the cervix (distal to the ovary). On the day fo llowing surgery simultaneous blood samples from cannulated vessels were col lected every 20 min for 3 hours. The concentration of steroid hormones was determined by radioimmunassay. The mean concentrations of studied hormones in branches of the uterine artery proximal and distal to the ovary were sig nificantly greater than in the jugular vein (P<0.001) by 18 to 69% and 7 to 31%, respectively. The concentrations of hormones in proximal and distal t o the ovary branch of the uterine artery were also significantly different (P<0.001). The increase in concentrations of the measured hormones did not differ considerably between investigated days of pregnancy. It is concluded that during maternal recognition of pregnancy, formation of the corpus lut eum of pregnancy, implantation of the embryo and the placenta elongation th e oviduct and uterus are supplied with locally elevated concentration of st eroid hormones compared to systemic blood. (C) 1998 by Elsevier Science Inc .